sign of infinity and isinf()?

[Steve Kargl]

Gang,

I don't have a copy of the C99 standard only Harbison and Steele,
5th Ed.  On page 440, they state: "The isinf macro returns a nonzero
value if and only if its argument is infinite (with any sign)."

The program below does note return the sign.
kargl[243] gcc -o a -O a.c
kargl[244] ./a
-inf
1



#include <stdio.h>
#include <math.h>

int main(void) {
	double x, y;
	x = -1.;
	y = 0.;
	x /= y;
	printf("%lf\n", x);
	printf("%d\n", isinf(x));
}


-- 
Steve